This invention relates to a telecine apparatus in which a video signal representative of picture information on a cinematographic film is generated, usually for subsequent use with a televison system. In such apparatus, light passing through image frames of the film is received by an electro-optical converter which generates an electrical signal in response thereto. The response characteristic of typical electro-optical converters is non-linear at very low light levels, and it has been proposed to shine a bias light on to the converter in addition to the image light so as to operate the converter on a more linear portion of its characteristic. To allow for variations in film density and film transport speeds and the like, it can be necessary to vary the strength of the light which illuminates the film and it is difficult to adjust the bias light in correspondence with such a variation so that the electrical video signal generated has uniform characteristics which result in the reproduction of television pictures having consistent quality with the correct black shading and contrast etc. The present invention seeks to provide an improved telecine apparatus.